2. HEAD OUTDOORS. Take that workout outside, and do it in the morning to get more of a boost. "Natural light suppresses the sleep-promoting hormone melatonin, making you feel more alert," says sleep specialist Ron Popper, M.D., of the Southern California Pulmonary and Sleep Disorders Medical Center.

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3. CHOP YOUR TO-DO LIST IN HALF. "Chronic worry raises stress hormones, which increases your blood pressure and heart rate and leaves you exhausted," says Judith Orloff, M.D., author of Emotional Freedom. Whittle down your to-do list to the essentials, and figure out a manageable way to take care of them. Then let the other, smaller stuff slide a little — and do something fun instead.

4. SIT UP STRAIGHT. Slouching leads to fatigue and back pain, both of which wear you out, says Daniel Mazanec, M.D., associate director of the Center for Spine Health in Cleveland. Set an hourly alarm on your computer as a reminder to straighten up.

5. SAY NO TO MS. NEEDY. After a call or visit with a friend, ask yourself if you feel energized or completely depleted. Limit time with "emotional vampires" (drama queens, narcissists — you know who they are) and focus on friendships that lift you up.